Re: Peu Expression Analyzer
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>I built a C compiler many years ago and used a non-recursive expression =
>analyzer because it was faster, and my head aches (still!) when I try =
to=20
>understand or debug recursive routines.
I an working on a script language. What makes this work so easy is that =
I practically don't have to write an expression analyzer. I can use some =
freeware expression evaluater (Calc Express w/source... 6 pages of code) =
to evaluate what is expressions for assignment. What I have to do is to =
parse what is left. In the script code below.. everything in RED is done =
by the expression evaluator (it handle parantheses and presedence very =
well).
Since the expression evaluation will basicly be the same for different =
languages, I think it was a good idea the make language and expression =
evaluation two separate modules.
Rom
A script language
var
i, j, a, b: Single;
v: array of Single;=20
procedure exitProc;
begin
Print( 'finished' );
end;
procedure main;
begin
a :=3D 100;
b :=3D 22.5 * (a / (1.05^3));
for i :=3D 1 to 10 do begin
for j :=3D 1 to a do begin
print( FloatToStr( i*10 + j));
end;
end;
a :=3D nil;
v( a + 19 ) :=3D 20;
b :=3D sysfunc( 2 * (100 + sin( v(10) + 10));
if ((a < 2) or (a > 5) ) and (v( 2) =3D 22.33) then begin
exit;
end
ifNot begin=20
exitProc; exit;
end
else begin // no conclusion
exitProc; exit;
end;
end;
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<BODY bgColor=3D#ffffff>
<DIV><FONT face=3DArial></FONT> </DIV>
<DIV><FONT face=3DArial>>I built a C compiler many years ago and used =
a=20
non-recursive expression </FONT></DIV>
<DIV><FONT face=3DArial>>analyzer because it was faster, and my head =
aches=20
(still!) when I try to </FONT></DIV>
<DIV><FONT face=3DArial>>understand or debug recursive =
routines.</FONT></DIV>
<DIV><FONT face=3DArial></FONT> </DIV>
<DIV><FONT face=3DArial></FONT> </DIV>
<DIV><FONT face=3DArial>I an working on a script language. What makes =
this work so=20
easy is that I practically don't have to write an expression analyzer. I =
can use=20
some freeware expression evaluater (Calc Express w/source... 6 =
pages of=20
code) to evaluate what is expressions for assignment. What I have to do =
is to=20
parse what is left. In the script code below.. everything =
in RED=20
is done by the expression evaluator (it handle parantheses and =
presedence very=20
well).</FONT></DIV>
<DIV><FONT face=3DArial></FONT> </DIV>
<DIV><FONT face=3DArial>Since the expression evaluation will basicly be =
the same=20
for different languages, I think it was a good idea the make =
language and=20
expression evaluation two separate modules.</FONT></DIV>
<DIV><FONT face=3DArial></FONT> </DIV>
<DIV><FONT face=3DArial>Rom</FONT></DIV>
<DIV><FONT face=3DArial></FONT> </DIV>
<DIV><B><FONT size=3D5>
<P align=3Dcenter>A script language</P></B></FONT>
<P><FONT face=3D"Courier New" size=3D2>var</FONT></P>
<P><FONT face=3D"Courier New" size=3D2> =
i, j,=20
a, b: Single;</FONT></P>
<P><FONT face=3D"Courier New" size=3D2> =
v:=20
array of Single; </FONT></P>
<P><FONT face=3D"Courier New" size=3D2>procedure exitProc;</FONT></P>
<P><FONT face=3D"Courier New" size=3D2>begin</FONT></P>
<P><FONT face=3D"Courier New" size=3D2> =
Print(=20
'finished' );</FONT></P>
<P><FONT face=3D"Courier New" size=3D2>end;</FONT></P>
<P><FONT face=3D"Courier New" size=3D2>procedure main;</FONT></P>
<P><FONT face=3D"Courier New" size=3D2>begin</FONT></P>
<P><FONT face=3D"Courier New" size=3D2> =
a :=3D=20
<FONT color=3D#ff0000>100</FONT>;</FONT></P>
<P><FONT face=3D"Courier New" size=3D2> =
b :=3D=20
<FONT color=3D#ff0000>22.5 * (a / (1.05^3))</FONT>;</FONT></P>
<P><FONT face=3D"Courier New" size=3D2> =
for i=20
:=3D <FONT color=3D#ff0000>1</FONT> to <FONT color=3D#ff0000>10</FONT> =
do=20
begin</FONT></P>
<P><FONT face=3D"Courier New" size=3D2> =
=20
for j :=3D <FONT =
color=3D#ff0000>1</FONT> to=20
<FONT color=3D#ff0000>a</FONT> do begin</FONT></P>
<P><FONT face=3D"Courier New" size=3D2> =
=20
=
=20
print( FloatToStr( <FONT color=3D#ff0000>i*10 + j</FONT>));</FONT></P>
<P><FONT face=3D"Courier New" size=3D2> =
=20
end;</FONT></P>
<P><FONT face=3D"Courier New" size=3D2> =
=20
end;</FONT></P>
<P><FONT face=3D"Courier New" size=3D2> =
a :=3D=20
<FONT color=3D#ff0000>nil</FONT>;</FONT></P>
<P><FONT face=3D"Courier New" size=3D2> =
v(=20
<FONT color=3D#ff0000>a + 19 </FONT>) :=3D <FONT =
color=3D#ff0000>20</FONT>;</FONT></P>
<P><FONT face=3D"Courier New" size=3D2> =
b :=3D=20
sysfunc(<FONT color=3D#ff0000> 2 * (100 + sin( v(10) + =
10)</FONT>);</FONT></P>
<P><FONT face=3D"Courier New" size=3D2> =
if=20
<FONT color=3D#ff0000>((a < 2) or (a > 5) ) and (v( 2) =3D =
22.33)</FONT> then=20
begin</FONT></P>
<P><FONT face=3D"Courier New"=20
size=3D2> &nbs=
p; exit;</FONT></P>
<P><FONT face=3D"Courier New" size=3D2> =
=20
end</FONT></P>
<P><FONT face=3D"Courier New" size=3D2> =
ifNot=20
begin </FONT></P>
<P><FONT face=3D"Courier New" size=3D2> =
=20
exitProc; exit;</FONT></P>
<P><FONT face=3D"Courier New" size=3D2> =
=20
end</FONT></P>
<P><FONT face=3D"Courier New"><FONT size=3D2> =
=20
else begin <FONT color=3D#0000ff>// no =
conclusion</P></FONT></FONT></FONT>
<P><FONT face=3D"Courier New" size=3D2> =
=20
exitProc; exit;</FONT></P>
<P><FONT face=3D"Courier New" size=3D2> =
=20
end;</FONT></P>
<P><FONT face=3D"Courier New" size=3D2>end;</FONT></P>
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